Rise from the Grave doesn’t overwrite any previous colors or types. Rather, it adds another color and another subtype.

10/1/2009

If the targeted creature is normally colorless, it will simply become black. It won’t be both black and colorless.

10/1/2009

A later effect that changes the affected creature’s colors will overwrite that part of Rise from the Grave effect; the creature will be just the new color. The same is true about an effect that changes the affected creature’s types or subtypes.

10/1/2009

A “creature card” is any card with the type creature, even if it has other types such as artifact, enchantment, or land. Older cards of type summon are also creature cards.